WO1997025278A1

WO1997025278A1 - Process for purifying rinsing water used in semiconductor manufacture

Info

Publication number: WO1997025278A1
Application number: PCT/CH1996/000442
Authority: WO
Inventors: Philippe Rychen; Thomas Kleiber; Dominique Gensbittel
Original assignee: Christ Ag
Priority date: 1996-01-04
Filing date: 1996-12-17
Publication date: 1997-07-17
Also published as: CN1200712A; NO981323D0; JPH11506700A; KR100421519B1; KR19990063887A; EP0876298B1; TW371295B; NO981323L; MY116594A; CA2231198C; CA2231198A1; CN1120130C; NO314993B1; EP0876298A1; ATE202327T1; US6123851A; DE59607144D1

Abstract

The hydrophilic organic impurities and hydrogen peroxide in rinsing water from semiconductor manufacturing processes are removed by adsorption on a pyrolysate of a macroreticular sulphonated vinyl aromatic polymer with a carbon content of at least 85 wt % and a carbon/hydrogen atomic ratio of 1.5:1 to 20:1. Despite their hydrophobic surface, the pyrolysates exhibit a high adsorbing capacity for these impurities and permit markedly higher removal rates than the usual active charcoals.

Description

Process for the treatment of rinse water from the

Semiconductor manufacturing

The invention relates to a method for removing hydrophilic organic contaminants from rinsing water in semiconductor production by means of adsorption.

In the manufacture of integrated circuits (chips), the wafers have to be rinsed with various chemicals and with high-purity water after certain operations, including after etching. The large amounts of flushing water (reclaim) has a quality due to the content of organic and inorganic substances, which makes direct recycling into the ultrapure water production cycle impossible. On the other hand, recycling of the rinsing water is made considerably more difficult by the organic impurities originating from the semiconductor production, since TOC values (total organic carbon content) of less than 5 ppb have to be achieved in the ultrapure water circuit and these organic impurities also have to be reached conventional methods such as reverse osmosis, mixed bed filters, degassing, UV radiation and ultrafiltration can usually only be removed to a sufficient extent.

Typical semiconductor rinse waters contain inorganic and organic substances, such as, for example, fluoride, chloride, nitrate, sulfate, phosphate and ammonium ions, hydrogen peroxide, isopropanol, acetone, N-methylpyrrolidone, tetramethylammonium hydroxide, methanol, ethanol, butanol , Acetic acid, dimethyl sulfoxide, propylene glycol methyl ether acetate and the like. The main components usually consist of isopropanol, acetone, N-methylpyrrolidone, hydrofluoric acid, Hydrochloric acid, sulfuric acid, phosphoric acid, hydrogen peroxide, ammonia, ammonium fluoride, tetramethylammonium hydroxide and the like. The rinsing water can typically have an electrical conductivity of approximately 10 to 2000 μS / cm and a TOC value of approximately 0.1 to 20 ppm. The pH is generally between about 2 and 9, mostly below 7.

For reasons of cost and environmental protection and for reasons of water scarcity, it is desirable to process these rinsing water, the total content of impurities of which is generally well below that of ordinary tap water, to such an extent that it can be used again in semiconductor production .

Today, ion exchange processes, reverse osmosis processes, adsorption on activated carbon, biological processes and ultrafiltration are used to process the rinsing water. For example, free mineral acids and organic acids are routinely removed via weakly or strongly basic anion exchange resins. In addition, reverse osmosis systems, some of which are already present in the make-up water purification of the ultrapure water systems, together with the ion exchange stages present are generally readily able to remove both inorganic and organic acids, bases and salts to a sufficient extent. Hydrogen peroxide and hydrophilic organic compounds such as isopropanol, acetone, N-methylpyrrolidone, methanol, ethanol, butanol, dimethyl sulfoxide and the like, however, are usually only separated to about 50-70% even in reverse osmosis stages, which in view of the required TOC Values of less than 5 ppb are far from sufficient. Additional treatment with activated carbon can the concentrations of these compounds are in principle further reduced; A satisfactory separation is often difficult or impossible to achieve even in this way.

The known methods therefore have the disadvantage that several cleaning methods have to be combined and nevertheless, especially in the case of comparatively high concentrations of organic impurities, often no satisfactory results can be obtained and / or biofouling is the stage downstream of a biological stage or an activated carbon filter can affect.

On the other hand, e.g. known from US-A-4040990, JP-A-62/197308, US-A-4839331, EP-A-0604110 and EP-A-0623557 by pyrolysis of synthetic polymers, kohlear¬ term adsorbents which have a compared to Aktiv ¬ have a more hydrophobic carbon surface and are therefore better able to adsorb hydrophobic organic compounds, in particular hydrocarbons and halogenated hydrocarbons, than activated carbon. Corresponding products are e.g. commercially available under the brand name Ambersorb (Rohm and Haas, Philadelphia, USA).

In EP-A-0285321 it was also proposed to use pyrolysates of crosslinked polymers as adsorbents for the separation of bacterial endotoxins (lipopolysaccharides), which may be present as pyrogens in tap water or in purified water, for example as a result of storage. Suitable crosslinked polymers are, for example, styrene-divinylbenzene copolymers which, if necessary, can be sulfonated or chloromethylated and then aminated to form an ion exchange resin. nen. As further disclosed in EP-A-285321, this method can also be used in water treatment processes in which high-purity water is produced and stored by bringing the stored water into contact with the pyrolysate before a subsequent filtration step. In this case, however, tap water is used for the production of ultrapure water and the adsorption step only serves to separate any pyrogens that may be present from the stored high-purity water.

Surprisingly, it has now been found that pyrolyzates of macroreticular sulfonated vinylaromatic polymers are able to adsorb the hydrophilic organic impurities and hydrogen peroxide present in the rinsing water of the semiconductor production much better than activated carbon, despite their more hydrophobic surface. In addition, it was found that impurities adsorbed on the pyrolysates mentioned are much better desorbable than adsorbed on active carbon.

The invention therefore relates to an adsorption process for removing hydrophilic organic impurities which are miscible with water at 15 ° C. in amounts of at least 10% by weight and / or hydrogen peroxide from rinsing water from semiconductor production, which is characterized by this that the rinse water is passed through a bed of a pyrolyzate of a macroreticular sulfonated vinyl aromatic polymer having a carbon content of at least 85% by weight and a carbon / hydrogen atomic ratio of 1.5: 1 to 20: 1. It has been shown that the process according to the invention not only achieves significantly better removal rates, but usually also the adsorption capacity of the pyrolysate is significantly higher than that of a conventional activated carbon. Even with a single adsorption stage with, for example, a column height (bed height) of 60 cm, removal rates of far more than 90% are generally achieved, which is particularly surprising as a good adsorption capacity of hydrophobic pyrolyzates for Hydrophilic compounds were not to be expected and the impurities in the rinse water were only present in amounts of a few ppm. With the method according to the invention, the required TOC values of less than 5 ppb can thus easily be achieved, if necessary by connecting two or more adsorption stages in series and / or preferably by combining them with the fresh water treatment methods already present. In addition, the pyrolysates which can be used according to the invention, in contrast to activated carbon, which is usually not regenerated, have the advantage that they can be regenerated easily.

In the context of the present invention, the term “hydrophilic organic impurity” denotes non-ionic organic compounds which can be present in rinsing water from semiconductor production and are miscible with water at 15 ° C. in amounts of at least 10% by weight, in particular non-ionic organic compounds which are liquid at 20 ° C., such as the isopropanol, acetone, N-methylpyrrolidone, methanol, ethanol, butanol, acetic acid, dimethyl sulfoxide and propylene glycol ether acetate, in particular isopropanol, acetone and, used in semiconductor production N-methylpyrrolidone. The term "vinyl aromatic polymer" in the context of the present invention denotes polymers obtained by polymerizing a vinyl aromatic monomer.

The term “macroreticular” is to be understood in the context of the present invention in such a way that the polymers in question to a large extent have pores with a pore radius of at least 25 nm.

The pyrolysates which can be used according to the invention expediently have a carbon content of at least 85% by weight and a carbon / hydrogen atomic ratio of 1.5: 1 to 20: 1, preferably 2: 1 to 10: 1. You can in a known manner, e.g. according to the methods described in US-A-4040990, US-A-4839331 and JP-A-62/197308, by controlled thermal degradation from macroreticular sulfonated vinylaromatic polymers.

Both homopolymers and copolymers of monoethylenically unsaturated monomers, such as styrene, vinyltoluene, ethylvinylbenzene, vinylxylene and vinylpyridine, and polyethylenically unsaturated monomers, such as divinylbenzene, trivinylbenzene, divinyltoluene and divinylpyridine, are suitable as starting polymers. In general, however, copolymers of a monoethylenically and a polyethylenically unsaturated polymer are preferred. Styrene-divinylbenzene copolymers are particularly preferred, in particular those obtained by polymerizing 75-90 parts by weight of styrene with 25-10 parts by weight of divinylbenzene.

The polymerization can be carried out by known methods, for example as described in US-A-4040990 and US-A-4839331 ben, take place. A preferred method is suspension polymerization disclosed in US-A-4224415.

The sulfonation of the polymers can also be carried out in a known manner, for example using concentrated sulfuric acid, oleum, sulfur trioxide or chlorosulfonic acid at elevated temperature. Suitable conditions are e.g. known from US-A-2366007, US-A-2500149, US-A-4224415 and US-A-4839331.

The pyrolysis of the sulfonated polymers, e.g. known from US-A-4040990 and US-A-4839331, by heating the polymers to a temperature of about 300-1200 ° C, preferably about 400-800 ° C, in an inert gas atmosphere (eg nitrogen, helium, neon and / or argon) for about 0.3 to 2 hours. If desired, an activating gas such as carbon dioxide, oxygen or water vapor can be added to the inert gas or an aftertreatment can be carried out by heating to about 300-1200 ° C in an activating gas. Pyrolysates that have not been treated with an activating gas, however, generally show better adsorption capacity for hydrophilic organic contaminants.

In the pyrolysis of the polymers, micropores are formed in addition to the pores present in the polymer, which are largely retained in the pyrolysis. According to the pore size definition of IUPAC, micropores with a pore radius of more than 25 nm, mesopores with a pore radius of 1 to 25 nm and micropores with a pore radius of less than 1 nm can be distinguished in the pyrolysate, the adsorption presumably predominantly in the Micropores take place, while the mesopores and macropores facilitate transport to the micropores.

In the adsorption process according to the invention such pyrolysates are preferably used, the macro pores having a specific pore volume of at least about 0, ₁ mL / g, preferably at least about 0.13 ml / g (for example 0,20- 0,25 ml / g), and mesopores with a specific pore volume of at least about 0.1 ml / g, in particular at least about 0.12 ml / g (for example 0.13-0.20 ml / g). Furthermore, pyrolysates are generally preferred which have micropores with a specific pore volume of at least about 0.1 ml / g, particularly preferably at least about 0.2 ml / g (for example 0.2-0.4 ml / g). The pore volumes mentioned correspond in each case to the values obtained from the nitrogen adsorption isotherms on a Micromeritics 2400 porosimeter. However, the pore volumes mentioned are not critical, and pyrolysates with smaller pore volumes are in principle also suitable.

Surprisingly, it was also found that the adsorption capacity of the comparatively hydrophobic pyrolyzates for the hydrophilic organic impurities present in the rinsing water of the semiconductor production apparently increases with increasing hydrophobicity of the pyrolysate surface. Pyrolysates, which are able to adsorb less than 300 mg water per g pyrolysate at room temperature (24 ° C.) and a relative air humidity of 94%, have proven to be particularly suitable in the process according to the invention for the adsorption of hydrophilic organic impurities, the best Results have been achieved with pyrolysates which are capable of adsorbing less than 200 mg of water per g of pyrolyzate. On the other hand, are suitable for the adsorption of hydrogen peroxide rather as comparably less hydrophobic pyrolysates, was to find that pyrolysates, the mg at room temperature (24 ^C C) and a relative humidity of 94% at least 200, examples game as 200-400 mg, preferably 200- 300 mg of water per g of pyrolysate are able to adsorb, are generally more suitable than those which are able to adsorb less than 200 mg of water per g of pyrolysate.

To remove hydrophilic organic impurities and hydrogen peroxide, two pyrolysates can therefore preferably be used, one of which is capable of adsorbing at least 200 mg of water and the other less than 200 mg of water per g of pyrolysate. The process can be carried out in such a way that the rinsing water is passed either through a bed of a mixture of the two pyrolysates or one after the other, in any order, through a bed of these two pyrolysates.

The pyrolysates are chemically, thermally and physically very stable. They generally have a specific surface area of about 100-2000 m ² / g, mostly about 500-1200 m ² / g, and can be, for example, in the form of approximately spherical particles with an average grain size of, for example, about 0.2 to 1.5 mm, preferably about 0.3 to 1.0 mm, can be used. Suitable pyrolysates are commercially available, for example, under the names Ambersorb 348F, Ambersorb 572, Ambersorb 575, Ambersorb 563 and Ambersorb 564 (Rohm and Haas, Philadelphia, USA), all of which are suitable for adsorbing hydrophilic organic contaminants and hydrogen peroxide. Preferably, however, for the adsorption of hydrophilic organic impurities, Ambersorb 563 and / or 564 and for the adsorption of Hydrogen peroxide Ambersorb 572 and / or 575 can be used.

The process according to the invention can be carried out by the methods customary for adsorption processes, the pyrolysate bed preferably being arranged in an adsorption filter or a column which can be operated in the upflow or downflow process. In general, a bed height of at least about 30 cm, for example about 60-150 cm, is recommended. In order to improve the removal rate, the bed height can be increased; In this case, however, it is generally more advantageous to connect two or more pyrolysate beds in series. A weakly basic anion exchanger can preferably be connected downstream of the pyrolysate bed.

When using fresh pyrolysates, it is advisable to pass deionized water through the pyrolysate bed for a few days before commissioning in order to hydrate the pyrolysate. Hot water is preferably first passed through the bed and the further treatment is carried out at room temperature.

If the pyrolysate is exhausted or the removal rate drops below a certain value, for example below 90%, the supply of rinsing water can be interrupted and the pyrolysate can be regenerated and reused in the normal flow or countercurrent process. The regeneration can preferably be carried out by passing water vapor through the pyrolysate at a temperature of about 100 to 250 ° C. Generally, less than about 12 bed vouchers are sufficient Lumens of steam (measured as condensate) in order to remove the adsorbed impurities as far as possible.

The flow rates can be, for example, about 5-40 bed volumes of rinsing water per hour during operation and about 0.1-2.0 bed volumes of water vapor (measured as condensate) per hour during regeneration.

In order to avoid interrupting the rinsing water treatment during the regeneration, two or three pyrolysate beds can preferably be provided, one or two of which are in operation while a bed is being regenerated.

The adsorption process according to the invention is further illustrated by the following example.

example 1

In four columns made of transparent polyvinyl chloride with a column diameter of 40 cm and a column height of 1.5 m, an adsorbent was filled up to a bed height of 60 cm (bed volume BV = 0.75 1), namely for comparison purposes (A) Amberlite XAD 16 (Rohm and Haas) and (B) the activated carbon Carbon BD (Chemviron) and, according to the invention, (C) Ambersorb 572 (Rohm and Haas) and (D) Ambersorb 563 (Rohm and Haas). For the purpose of hydration in the column, the fresh adsorbents were flowed through for 7 days with deionized water at a flow rate of 1 l / h. Subsequently, water containing about 10-20 ppm hydrogen peroxide and a TOC content of 5.2-6.5 ppm consisting of acetone and isopropanol in a weight ratio of 1: 1 was in each case at a temperature of 20-22 ° C. With at a flow rate of 5 BV / h through the columns and the TOC value and the content of hydrogen peroxide in the escaping water were measured. The water supply was interrupted overnight. The TOC values in the feed and the determined adsorption capacities until the removal rates dropped to 90% are given in Table 1 together with the percentage removal rates for hydrogen peroxide (degradation of H ₂ 0 ₂ in%). The TOC removal rates as% adsorption based on the TOC values in the feed are shown graphically in FIG. 1 against the bed volumes of water supplied. As the results show, significantly higher TOC removal rates are achieved with the pyrolysates used according to the invention, and they also have higher absorption capacities.

Table 1

Claims

claims

1. Process for the removal of hydrophilic organic impurities which are miscible with water at 15 ° C in amounts of at least 10% by weight, and / or of hydrogen peroxide from rinsing water of semiconductor production by means of adsorption, characterized in that the rinsing water through a bed of a pyrolyzate of a macro reticular sulfonated vinyl aromatic polymer with a carbon content of at least 85% by weight and a carbon / hydrogen atomic ratio of 1.5: 1 to 20: 1.

2. The method according to claim 1, characterized in that one uses a pyrolysate, the macropores with a pore radius of more than 25 nm and a specific pore volume of at least 0.1 ml / g and mesopores with a pore radius of 1 to 25 nm and a specific pore volume of at least 0.1 ml / g.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that one uses a pyrolysate, the macropores with a pore radius of more than 25 nm and a specific pore volume of at least 0.13 ml / g and mesopores with a pore radius of 1 to 25 nm and a specific pore volume of at least 0.12 ml / g.

4. The method according to any one of claims 1 to 3, characterized in that a pyrolysate is used which has micro pores with a pore radius of less than 1 nm and a specific pore volume of at least 0.1 ml / g.

5. The method according to any one of claims 1 to 4, characterized ge indicates that a pyrolysate is used which has micro pores with a pore radius of less than 1 nm and a specific pore volume of at least 0.2 ml / g.

6. The method according to any one of claims 1 to 5, characterized ge indicates that a pyrolyzate with a carbon / hydrogen atom ratio of 2: 1 to 10: 1 is used.

7. The method according to any one of claims 1 to 6, characterized in that one uses a pyrolyzate, which

Air at room temperature and a relative humidity of 94% is able to adsorb less than 300 mg of water per g of pyrolysate.

8. The method according to any one of claims 1 to 7, characterized in that a pyrolysate is used to remove hydrophilic orga¬ nical impurities, the air from air at room temperature and a relative humidity of 94% less than 200 mg of water per g can adsorb pyrolysate.

9. The method according to any one of claims 1 to 8, characterized ge indicates that a pyrolysate is used to remove hydrogen peroxide, which from air at room temperature and a relative humidity of 94% to at least 200 mg of water per g of pyrolysate can adsorb.

10. The method according to any one of claims 1 to 9, characterized ge indicates that a pyrolysate of a styrene-divinyl benzene copolymer is used.

11. The method according to any one of claims 1 to 10, characterized in that a pyrolysate of a styrene-divinyl nylbenzene copolymer with a weight ratio of styrene / divinylbenzene of 75-90: 10-25 is used.

12. The method according to any one of claims 1 to 11, characterized in that one uses a pyrolysate with an average grain size of 0.2 to 1.5 mm.

13. The method according to any one of claims 1 to 12, characterized in that the supply of rinsing water is interrupted for the regeneration of the pyrolysate and water vapor is passed through the pyrolysate bed at a temperature of 100 to 250 ° C.